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Engineering Evaluation of Hesco Barriers Performance at Fargo_ ND

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Engineering Evaluation of Hesco Barriers Performance at Fargo_ ND Powered By Docstoc
					                                 ENCLOSURE 2

Wenck Associates, Inc., "Engineering Evaluation of Hesco Barriers Performance at
                           Fargo, ND 2009," May 2009
                                           Engineering
                                   Evaluation of Hesco
                                  Barriers Performance
                                     at Fargo,ND 2009




          Wenck File #2283-01




                  Prepared for:

        Hesco Bastion, LLC
47152 Conrad E. Anderson Drive
          Hammond, LA 70401


                  Prepared by:

WENCK ASSOCIATES, INC.
      3310 Fiechtner Drive;
                  Suite 110
       Fargo, North Dakota
                                                May 2009
            (701) 297-9600

                                       SWenck
                                                Table of Contents

1.0   INTRODUCTION ...........................................................................................................                        1-1

        1.1        Purpose of Evaluation.........................................................................................                     1-3
        1.2        Background Information ......................................................................................                      1-3

2.0   CITY OF FARGO USES OF HESCO BARRIERS .........................                                                                                  2-1

       2.1         Number of Miles Used Versus Total ...................................................................                              2-1
       2 .2        S izes ........................................................................................................    .............   2 -1
       2.3         Installation Rates ..................................................................................................              2-1
       2.4         Complicating Factors ..........................................................................................                    2-1

3.0   INTERVIEWS WITH CITY AND CITY REPRESENTATIVES .............................                                                                     3-1

       3.1         Issues Raised and Areas of Concern ....................................................................     3-1
       3.2         Comments from Interviews .....................................................  ........................... 3-1

4.0   ON SITE EVALUATIONS BY WENCK ASSOCIATES, INC ..................................                                                                 4-1

       4.1         Visual Inspection .................................................................................................                4-1

5.0   TECHNICAL EVALUATIONS .....................................................................................                                     5-1

       5 .1        S lid ing .................................................................................................................        5 -1
                   5.1.1       Review of Available Information ..........................................................                             5-1
                   5.1.2       Independent Review ..............................................................................                      5-3
                   5.1.3       Field Testing .........................................                                                                5-4
       5.2         Overturning/Tipping ............................................................................................                   5-8
       5 .3        S eep age ...............................................................................................................          5-9
                   5.3.1 Review of Available Information ...............................................................                              5-9

6.0   SUM MARY AND RECOMMENDATIONS ................................................................                                                   6-1




                                                                          1
ATTACHMENTS

A - Red River Flood Protection Plan - 3/26/2009
              (Map of Levee System)

B - "Engineering Analysis" from Report to:
              United States Senate Committee on Appropriations, June 29-30, 2004.




                                             ii
                                      1.0                      Introduction


The Fargo, North Dakota area, along with its sister city across the river, Moorhead, Minnesota
was recently faced with massive flooding from the Red River of the North. Due to an unusually
wet fall, followed by a cold, snowy winter, the normally placid Red River was forecasted by the
National Weather Service (NWS) to reach a flood crest elevation of 37 to 39 feet in Fargo by late
March.(1 ) Unfortunately, unusual conditions continued to dominate, forcing the NWS to revise
their forecast up to 41 feet, higher than any flood level on record, and predicted for only 7 to 10
days from then, instead of the originally estimated three weeks. As the river rapidly rose to
nearly 39 feet, new forecasts predicted the river might even go as high as 42 or even 43 feet.


This situation, of course, generated intense concerns, and forced the rapid evaluation and
subsequent use of several different methods of flood protection. To protect the City of Fargo,
temporary clay dikes, which are the most common form of flood protection in the area, were
used to the greatest extent possible to raise existing flood protection to at first 42 feet, but later
raised to 44 feet in response to the revised forecasts. Traditional sandbag dikes were also widely
used, but due to time constraints, reliability, height limitations, and availability of volunteers, the
length of dikes that could be deployed could not meet all the area needs. Therefore, the US
Army Corps of Engineers, who were assisting the City of Fargo, turned to Hesco Bastion, LLC
for help, and to provide the remaining flood barriers. Hesco barriers have been well-tested by
the U.S. Army Corps of Engineers (COE) for use as temporary flood protection, and widely used
in many flood situations around the country, including New Orleans for temporary hurricane
protection.



Footnote: (1) For reference, "normal" flood stage here is considered to be anything over 18 feet. The 1997 flood, called the
"Flood of the Century" and which inundated Grand Forks that year, reached a stage height in Fargo of 39.6 feet. The highest
level on record was 40.1 feet, reached back in 1897.




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Hesco barriers are able to be installed relatively quickly, and due to this speed of deployment,
approximately 10 miles of barriers were installed over a 4 to 5 day period. Fortunately, the
combination of clay dikes, sandbag dikes, and Hesco barriers, together with the tremendous
efforts by City of Fargo staff, National Guard, and volunteers, worked, and the City of Fargo
largely escaped serious flooding.


In the aftermath of these efforts, various comments surfaced regarding the performance of the
Hesco Barriers. In particular, concerns were raised about the possibility of the Hesco's sliding
laterally over the ground surface due to water pressure, and the increased rate of seepage through
the barriers over expected rates. Also, concerns were raised about two specific locations where
Hesco's had been deployed, and significant leakage had occurred requiring emergency actions to
prevent possible breaching.


Hesco Bastion, concerned about these comments, approached Wenck Associates, Inc. (Wenck)
to provide an independent engineering evaluation of the performance of the Hesco barriers
during the Fargo floodfighting efforts. The scope of this engineering evaluation was agreed to
be as follows:

        •     Meet with Mr. Dennis Barkemeyer of Hesco Bastion to discuss installation procedures
              that were used at the various sites in Fargo.

        *     Evaluate photographs taken during installation of the barriers.

        *     Visit selected Hesco sites around Fargo to evaluate post-flood barriers.

        *     Interview City of Fargo/COE staff to discuss product use, problems they encountered
              or noted, comparison to other dikes (sand bag and clay), and comments on the products.

        *     Revisit dike locations where the City/COE indicated they had problems or issues.

        *     Evaluate product and its uses in Fargo for floodfighting in light of the frozen ground
              oftentimes encountered, and the soft clay soils.

        *     Prepare a letter report or technical memorandum that outlines the findings of the above
              work, and provides recommendations for future use in this environment.

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   1.1     PURPOSE OF EVALUATION
           This independent engineering evaluation was requested by Hesco Bastion, LLC to
           address comments raised after Hesco units were installed in Fargo, North Dakota for
           combating flooding by the Red River of theNorth in March, 2009.


   1.2     BACKGROUND INFORMATION
           Hesco Bastion Concertainers® (hereinafter referred to as "Hesco"), are a structural
           system of linked baskets containing fill material. They provide a way of positioning and
           containing large volumes of earth, sand, gravel, or rock to form either temporary or long
           term structures. They may then be used for a variety of projects, including emergency
           flood protection (as at Fargo, North Dakota in 2009). The units are manufactured in
           various sizes and are made of welded galvanized steel mesh that are assembled with
           coiled joints. A polypropylene, nonwoven geotextile liner retains the fill material that is
           placed into the open top basket. The baskets are initially flat-packed on pallets, then
           extended and joined with joining pins, filled with fill material, and placed in various
           configurations depending on the end use. The units are lightweight, portable, and are
           easily deployed.




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         2.0                          City of Fargo Uses of Hesco Barriers


  2.1      NUMBER OF MILES USED VERSUS TOTAL
           The City of Fargo constructed a total of approximately 80 miles of dikes using a
           combination of clay, sandbags, and Hesco barriers. There were approximately 10 miles of
           Hesco barriers deployed within the City of Fargo. The barriers were used for both
           primary and contingency dikes, and were placed on paved and non-paved surfaces, as
           well as on top of existing levees. The location and types of dikes are shown in
           Attachment A.


  2.2      SIZES
           The City of Fargo deployed two types of Hesco units, the standard and flood barriers in
           the 3' deep by 3' high by 15' long, and 3' deep by 4' high by 15' long sizes. The standard
           barriers have separation fabric dividing each barrier into five equal compartments, 3'
           long each. The flood barriers do not utilize the separation fabric between compartments,
           so each unit is able to have continuous fill material.


  2.3      INSTALLATION RATES
           Installation rates varied greatly due to the availability of fill material, and the access to
           the area in terms of both men, equipment, and physical access. Field personnel that were
           interviewed stated they typically could deploy and fill 400 to 600 feet of Hesco's per
           hour.


  2.4      COMPLICATING FACTORS
           The City of Fargo is located in the Red River Valley, formed at the bottom of former
           glacial Lake Agassiz. This lake deposited thick sequences of lacustrine clays and silts,
           which form the soils here. These soils are very fertile, but have poor engineering
           properties, and are prone to slippage and soil failures. Weather conditions prior to the

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           rising of the Red River had completely saturated these soils, making conditions very
           muddy. Dikes then had to built on top of, and using, these saturated clay soils, often
           while rains continued. Subgrade conditions were thus far from ideal.


           Later in the week prior to the predicted flood crest for the Red River, the weather
           changed again to very cold, and the area received nearly one foot of snow. These cold
           conditions persisted fdr awhile, and caused many of the soils to freeze at the surface,
           further complicating subgrade conditions on which the Hesco barriers (and all temporary
           dikes) were built.




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                   3.0                Interviews with City and City
                                       Representatives


   3.1     ISSUES RAISED AND AREAS OF CONCERN
           During interviews with personnel involved with the Hesco barriers, concerns were
           brought up about the stability of the barriers. Some had thought that the barriers were
           kicking out at the bottom, leaning and possibly sliding over the soil surface. Comments
           were made about lines of Hesco barriers installed "straight", but then becoming ragged
           looking over subsequent days as though some were sliding and/or leaning, even though
           *no floodwater had reached them as yet. Concerns were also raised about possible sliding
           and/or overturning of the Hesco barriers if floodwaters came up over their half-way level
         * (approximately 2 feet vs. the 4-foot height of the barriers), especially since many were
           already leaning toward the water (although not installed with a noticeable "lean").
           Additionally, seepage through some of the barriers had caused some concern.


           Two specific locations of concern were also brought up by the City of Fargo. The first
           was on 5th Street South (just south of 1-94), and the second was along the south side of
           Drain 27 (just east of 1-29). It was stated that the   5 th   Street area had to be buttressed with
           material on the back side of the Hesco barriers and a section of sandbag dike, after a
           significant leak was found in the transition area from Hesco barrier to sandbag dike. The
           second was the Drain 27 area, which had shown settlement in one area where the Hesco
           barriers were placed on top of an existing earthen levee.


   3.2     COMMENTS FROM INTERVIEWS
           After hearing the above issues, Wenck interviewed several engineers that were directly
           involved in erecting Hesco barriers during the flood fight, as well as clay or sandbag
           dikes. These engineers included representatives from the City Engineering Department,
           and local firms, Ulteig Engineers, and SRF Engineers. Questions were asked directly

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           about the issues raised above, and what the engineers observed, as well as about the two
           locations of concerns.


           The first location of concern, 5th Street South, was thought to be a problem due to a
           sandbag dike being butted up directly to a Hesco barrier, with little or no overlap. This
           transition area had started to leak, so emergency crews buttressed the back side with clay
           to stop the excessive leakage. Field personnel thought the problem was due to the poor
           transition, not the Hesco units.


           The second location of concern, along the south side of Drain 27, was due to water
           pushing through a stormwater structure .and discharging rapidly out the top of a manhole.
           This water saturated the dike around the structure and caused a section of the dike to
           slump (sag), including the Hesco units on top of the dike. Field personnel packed clay
           over the top of the manhole, and built a small cofferdam around it to stop the leakage.
           Field personnel thought this issue had nothing to do with the Hesco units, only the
           stormwater structure.


           Field personnel indicated that the amount of dikes constructed with the Hesco barriers in
           a short time was instrumental in protecting the city. Building the 10 miles with sandbag
           dikes would have been very difficult with the time and volunteers available, plus the
           miles already built with sandbags. Additionally, the uniformity of the dikes erected with
           Hesco units was thought to be very important, especially relative to sandbag dikes raised
           on an emergency basis by volunteers. They also noted that the units adapted to terrain
           changes very well. Most thought that seepage under the units was less than what a
           sandbag dike would be, even without the poly-sheeting used in most locations. Field
           personnel believed that any leaning or apparent sliding of the units was most likely due to
           settlement of the units into the saturated clay subsoils, as subgrade locations were often
           poor due to the saturated conditions, and then the snow and freezing conditions, rather
           than actual sliding.




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                       4.0 On Site Evaluationsby Wenck Associates,
                                           Inc.


   4.1      VISUAL INSPECTION
            Visual observations were made of Hesco barrier installations at 5 th Street South, Drain
            27, the Fargo Country Club golf course, 40h Avenue South, Timberline addition, and the
            Harwood Groves area.


            The 5 th Street Hesco barriers were difficult to inspect for the concerns that were brought
           up by City staff. The area behind the Hesco barriers and sandbag dike had been filled in
           with sand after issues were first brought up. During interviews with field personnel it was
            determined that this area most likely didn't have the sandbag dike tied in sufficiently to
           the Hesco barriers. It was stated that the sandbags butted up directly to the Hesco units,
            instead of using a sufficient overlap to adequately protect the transition.


            In the Drain 27 area, Hesco barriers were placed on top of an existing earthen levee.
            Settlement was noted in a section of the earthen levee just east of 1-29 on the south side
            of the drain. Interviews and inspection showed that this appeared to be due to an existing
            storm sewer running through the existing earth levee and discharging to the drain. After
            installation of the Hesco barriers and noticeable settlement in part of the dike, it became
            apparent that a storm sewer structure located within the earthen levee was discharging
           water through the top of the structure and onto the earthen levee. This leakage completely
            saturated the area and allowed the Hesco barriers to settle into the earthen levee, as well
            as causing settlement of the levee itself.


            The Fargo Country Club area consisted of Hesco barriers being deployed through the
            golf course. Evidence of soft soils were noted from the ruts left by equipment used to
            deploy and fill the Hesco barriers.

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            The 40th Avenue south area had Hesco barriers installed on top of an existing earthen
            levee. A concern of the barriers leaning was made during interviews. Measurements
            showed that the barriers were leaning approximately 3.5" in 4 vertical feet. These barriers
           have also settled on the water side approximately a '/2", and none on the dry side.


            The Timberline area consisted of Hesco barriers that were used for primary temporary
           protection. Barriers were placed in residential backyards along a drainage channel. It was
           noted that some of the Hesco barriers were leaning. Measurements were made at a few
            locations, which showed 6.5" of lean in four feet. Field personnel indicated that the
           barriers were leaning during installation because of the lay of the land, and that they had
           performed field measurements over a couple of days and determined that the units had
           not shown any movement.


           The Harwood Groves area consisted of Hesco barriers installed in a 2 - 1 configuration
           (base 2 barriers wide with a single unit placed on top). The Hesco barriers were providing
            secondary protection is this area. Clay had been placed up to the top of the base units on
           the backside.




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                                           5.0 Technical Evaluations


           This section discusses three different traditional failure mechanisms for retaining
           structures such as the Hesco barriers; sliding, overturning/tipping, and seepage, and the
           Hesco barriers resistance to them. Within each of this subsections, references to previous
           studies are introduced and discussed (if available), followed by an independent review.


   5.1     SLIDING
           Sliding of a retaining system (i.e., the Hesco barriers) is most simply defined by Equation
            1, which relates the resisting and driving forces for sliding to the overall factor of safety
           against sliding. For long-term situations (i.e. permanent walls), it is considered good
           practice to have a factor of safety (FS) against siiding equal at least 1.5, meaning that the
           resisting forces are 50% greater than the driving forces. For short-term situations,
           applicable to temporary flood protection dikes, this acceptable, factor of safety is 1.3.


            FS   =   Resisting Forces                (Fv tan 6) + cL          (Equation 1)
                      Driving Forces                       Fh


           Where:                     Fv = Weight of basket (1' "slice" of basket) minus uplift force (lbs/ft)
                                      6= Interface friction coefficient
                                      c = Cohesion, or undrained shear strength (lbs/ft2)
                                      L    =   Length, or basket depth (ft)
                                      Fh   = Horizontal force from water (lbs/ft)


5.1.1      Review of Available Information
           A report issued for the United States Senate Committee on Appropriations, dated June
           29-30, 2004, discussed possible sliding, and is provided in Attachment B for reference.
           This report discusses the resistance to sliding based on different types of fill soils (fine



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           sand, coarse sand, and gravel), and different types of surfacing materials (earth, concrete,
           and grass).


           Table 1 of the referenced report, shown below, gives the interface coefficients of friction
           for the fill soils and surfacing materials.


           Table 1. Interface friction information

                                                                     Interface Coefficient of Friction
             Fill Type                              Earth                            Concrete                    Grass
                                            tan 8              8              tan 8             8        tan 8              5
            Fine Sand                        0.58              30             0.35              19       0.30               17
            Coarse Sand                      0.67              34             0.45              24       0.35               19
            Gravel                           0.78              38             0.60              31       0.40               22
           Note: tan 8 = Tangent (5)   =   p or the friction coefficient.

           Using the above information, the authors of the referenced report compiled factors of
           safety against sliding for 30 different load cases, considering various structure heights,
           flood heights, fill types, and surfacing materials. This information is provided in
           Attachment B, but most of the cases are shown again (albeit in a different order) in Table
           2 below. Information not included in Table 2 are the cases where the flood height was
           higher than the structure height, and also cases where the fill material was gravel
           (because site observations in Fargo noted that only sand was used to fill the Hesco
           Concertainers).


           Table 2. Factor of safety against sliding for various load cases organized by flood
                    height'

             Case 1 Flood Height       1 Structure
                                          Height                Surface
                                                             I.Type                   I Fill Type    FS (full
                                                                                                     uplift)          Iuplift) (no
                                                                                                                           FS

             4                  3                                  Concrete            Fine sand                             1 )     I
                                3                   3
                                                    3              Concrete            Fine sand                  l
             4
             5                  3                   3              Concrete           Coarse sand
             1                  3                   3                Earth             Fine sand
             2                  3                   3                Earth            Coarse sand
             7                  3                   3                Grass             Fine sand
             8                  3                   3                Grass            Coarse sand

             13                 3                   4              Concrete            Fine sand
             14                 3                   4              Concrete           Coarse sand
             10                 3                   4               Earth              Fine sand
             11                 3                   4               Earth             Coarse sand

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             Case        Flood Height   Structure        Surface         Fill Type         FS (full         FS (no
                                         Height           Tvye                             uplift)          unlift)
             16                3            4             Grass          Fine sand
             17                3            4             Grass         Coarse sand

             22                4            4            Concrete        Fine sand
             23      1         4            4        1   Concrete    I Coarse sand I
             19                4            4             Earth          Fine sand
             20                4            4             Earth         Coarse sand
             25                4            4             Grass          Fine sand
             26                4            4             Grass         Coarse sand
               Red highlighting means the factor of safety is not acceptable (below 1.0).
               Yellow highlighting means that the factor of safety is only marginally acceptable (between 1.0 and 1.3)
               Blue highlighting means that the factor of safety is acceptable (greater than 1.3) for short-term
               conditions.

           This table indicates that the authors found acceptable or marginally acceptable factors of
           safety against sliding are achievable for many of the cases analyzed, including all of the
           cases where the flood height was 3 feet, the containers were 4 feet high, and the
           containers were placed on earth.


5.1.2      Independent Review
           The above calculated factor of safety values assume that uplift pressures exist and will
           reduce the available resisting force. This is a conservative opinion, because it is likely
           that even if a layer of sand is frozen at the base of the Hesco Concertainer, enough pore-
           water pressure would be dissipated so as to minimize or negate the resulting uplift
           pressures (from buoyancy of the structure vs. the underlying soils), simply based on the
           fact that the drainage path for seepage beneath the unit is no longer than about 3 feet.


           An analysis was also completed for a two layer Hesco system (consider a double
           container base and a single container top) using the same theories as used to develop
           Table 2 (i.e., forces acting on a one-foot cross-section of barrier). This information is
           provided in Table 3, below.




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           Table 3. Factor of safety against sliding for various load cases organized by flood
                    height" 2

                                             Structure     Surface                           FS (full          FS (no
             Case      Flood Height                                         Fill Type          -niWA      I      nlifN   I
                                              Height        Type
             4                  6                6         Concrete         Fine sand
             5                  6                6         Concrete        Coarse sand
             1                  6                6          Earth           Fine sand
             2                  6                6          Earth          Coarse sand
             7                  6                6          Grass           Fine sand
             8                  6                6          Grass          Coarse sand

             13                 7                8         Concrete         Fine sand                            ý   I   i
             14                 7      ___
                                                 8 ___     Concrete    +
                                                                           Coarse sand
             10                 7                8          Earth           Fine sand
             11                 7                8          Earth          Coarse sand
             16                 7                8          Grass           Fine sand
             17                 7                8          Grass          Coarse sand

             22                 8                8         Concrete         Fine sand
             23                 8                8         Concrete        Coarse sand
             19                 8                8          Earth           Fine sand
             20                 8                8          Earth          Coarse sand
             25                 8                8          Grass           Fine sand
             26                 8                8          Grass          Coarse sand

           (1) Red highlighting means the factor of safety is not acceptable (at or below 1.0).
                 Yellow highlight means that the factor of safety is only marginally acceptable (between 1.0 and 1.3).
                 Blue highlighting means that the factor of safety is acceptable (greater than 1.3) for short-term
                 conditions.
           (2)   Overall system is set up as 2 containers on the bottom and one on top.


           This table shows that careful engineering is needed before installing such a two-tier
           system, as acceptable factors of safety are achievable for much fewer cases than the
           single tier system. These relatively low calculated factors, together with some concerns
           about the single tier system, especially with flood height equal to barrier height, showed
           that some actual field testing of the barriers should be done. This was largely due to
           actual field experience not squaring well with theory.


5.1.3      Field Testing
           In response to the concerns raised above, field test analyses were performed on partial
           sections of the Hesco units to determine the sliding resistance to lateral forces. These
           analyses were done in Fargo on April 9, 2009, and reported on in a separate technical

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           memo to Hesco Bastion LLC, dated April 30, 2009. Tests on 3' deep by 3' wide by 4'
           high sections were conducted with the filled units placed on various base surfaces. The
           total amount of force required to move the unit was recorded, along with the volume and
           weight of the filled unit. This allowed the actual friction coefficient and factor of safety
           to be computed in a real-life environment. An independent soils laboratory performed
           .soil analyses on submitted fill samples, and gave a unit weight and gradation of the fill
           sand for both uncompacted and medium compacted samples (see Tables 4, 5 and 6).
           [Note: The field tests did not consider overturning, bearing capacity of the underlying
           soils, or seepage rates of the units.]


Table 4. Field Data Collected

                                                       Basket     Basket       Calculated      Calculated
                                                       Weight     Weight         Friction        Friction
                               Hesco Unit     Load     @ 89.5     @ 102.0      Coefficient     Coefficient
 Test               Test       ("Basket")      Cell     PCF        PCF          if Sand is      if Sand is
 Surface             #           Volume      Reading    Sand       Sand         89.5 PCF       102.0 PCF
                                      (ft)    (Ibs)     (Ibs)       (Ibs)

 Grass                1               48.8    2700     4387         4978           0.62            0.54

 Grass -
 Muddy                2               44.0    3300      3956        4488           0.83            0.74

 Grass -
 Muddy/
 Saturated            3               51.4    3400      4621        5243           0.74            0.65

 PCC
 Street               4               46.7    2700      4198        4763           0.64            0.57

 PCC
 Street               5               49.8    2600      4477        5080           0.58            0.51
Notes: Weights of sand are from laboratory tests on samples obtained during field testing - 89.5 PCF is average
uncompacted, and 102.0 PCF is average of compacted samples to approximately 88% Standard Proctor.
PCF = Pounds per Cubic Foot
PCC = Portland Concrete Cement




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Table 5: Summary of Factor of Safety Calculations for Water 3' High Against 3' x 3' x 4'
High Baskets


                                                                                     Force
                                                                                    Causing
                                                 Forces Resisting Sliding            Sliding

                                      Basket         Fuplift                            F,
                                      Weight       (y, x Hx                         (y, x H2 x   Factor of
         Test Surface                 (ys x V)       w2/2)           A       FR        w)/2       Safety
                                       (Ibs)         (Ibs)                  (Ibs)      (Ibs)
 Grass                                 4387          842         0.58       2056       842         2.44
 Grass - Muddy                         3956          842         0.78       2429       842         2.88
 Grass -
 Muddy/Saturated                       4621           842        0.70       2645       842         3.14
 PCC Street                            4338           842        0.58       2028       842         2.40


Table 6: Summary of Factor of Safety Calculations for Water 4' High Against 3' x 3' x 4'
High Baskets


                                                                                     Force
                                                                                    Causing
                                                 Forces Resisting Sliding           Sliding

                                      Basket    Fuplift                                 Fw
                                      Weight (yw x H x                              (Yw x H x    Factor of
         Test Surface                 (ys x -V) w2/2)                L       FR        w)/2       Safety
                                        (Ibs)   (Ibs)                       (Ibs)      (Ibs)
 Grass                                  4387    1123             0.58       1893       1497        1.26
 Grass - Muddy                          3956    1123             0.78       2209       1497        1.47
 Grass -
 MuddylSaturated                       4621          1123        0.70       2449      1497         1.63
 PCC Street                            4338          1123        0.58       1865      1497         1.24




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     1) Summary of Calculated Friction Coefficient Data

                 Friction coefficients were calculated for each of the field tests performed.


                 The field data showed significantly higher friction coefficients than the original
                 engineering calculations, which used published friction coefficients for the different
                 base materials. This is believed to be due to the deformation of the bottom edge of the
                 basket, which was observed as it began to slide. This deformation cannot be
                 discounted, however, as it would occur in the event that the lateral loads applied to
                 the basket were enough to cause lateral movement. Therefore, the field measured
                 friction coefficients are believed to be valid for the specific situations in which the
                 baskets were tested.


                 These higher friction coefficients, in turn, show that the actual performance of the
                 Hesco units in resisting sliding is higher than the calculated resistance using
                 published friction coefficients, as shown by the factors of safety calculated in Tables
                 5 and 6.




                                                      5-7
U:\2283\01\Hesco Bastion Report.doc
   5.2      OVERTURNING/TIPPING
            Traditional methods of overturning analysis are not truly applicable for this type of
            container because of the general deformability of the system, plus the possibility that
            uplift pore-water pressures can often be dissipated
            through the sandy infill material. Even if a layer
            of sand is frozen at the base of the Hesco                                                 7.o.

            Concertainer, enough pore-water pressure would
            be likely dissipated so as to minimize or negate the
            uplift pressures, simply based on the fact that the
                                                                              1.30      EE'[0.25              FEET
                                                                        1.30 FEET
            drainage path is no longer than about 3 feet.
                                                                               RESISTING     DRIVING

            Therefore, the overturning and tipping will most                        BLOCK    BLOCK

            likely be related to either 1) installation issues (where infill material is placed in a manner
            such that initial container tilt occurs), or 2) thaw of the subsoil on only one side of the
            container occurs, such that some differential settlement occurs (e.g., rising water on one
            side of barrier thaws the soil beneath one side).


            As discussed earlier in this report, some of the units were experiencing some tilt, with
            angles nearing 6 or 7 degrees. Based on information obtained during the field work, it is
            believed that the units showing some tilt were either installed that way, or settlement of
            the units into the base soils occurred.


            For a single layer system, a tilt of less than 14 degrees is a reasonable maximum value.
            The reason for this is because the system tends to operate as a block. Therefore, at an
            angle of 14 degrees or less, there is at least 7 times the mass holding back the container
            from tipping. When considering this angle, the resisting mass and the associated moment
            arm of the units, based on the resisting and driving forces, a calculated system factor of
            safety against overturning is greater than 30. This is shown by Equation 2 below.
            Overturning or tipping is not considered to be a significant problem, therefore, unless the
            entire subgrade fails.
                                                      5-8
U:\2283\01\dtesco Bastion Report.doc
           FS = Resisting Forces
                 Driving Forces
                                                           x Density
           FS- Resisting Block Area x Resisting Moment Arm
                Driving Block Area x Driving Moment Arm x Density                (Equation 2)



  5.3      SEEPAGE
           Field personnel's input on the issue of seepage by the Hesco barriers varied greatly.
           Some thought that the seepage was excessive, while others thought it was less than a
           traditional sandbag levee would be. Most areas had poly-sheeting placed on the wet side
           of the Hesco units. However, an area of Drain 27 did not receive poly-sheeting, and the
           field staff thought that the seepage wasn't excessive and was easily managed.


           Assessment of actual seepage rates in the field were not part of this report.


.5.3.1 Review of Available Information
           In 2004, the USACOE conducted tests on Hesco units in regards to seepage rates. These
           initial tests showed higher seepage rates than other levee systems. Most of the seepage
           occurred through the seams between adjacent units. Hesco learned after these test that the
           end panels on adjacent units should be removed to decrease the amount Of seepage.
           Retesting of the units for seepage rates was conducted by USACOE in July and August,
           2005. In this retest, the end panels of units butted up against on another were removed.
           This allowed for a continuously filled sand unit with no gaps between units. This retest
           showed seepage rates of 0.04 gpm/ft at 1' of head, and 0.14 gpm/ft and a head of 2.85'




                                                    5-9
UA2283\01\-esco Bastion Report.doc
                                  6.0 Summary and Recommendations



Overall, the consensus of opinion among users of the Hesco barriers for the Fargo floodfight is
that the barriers are well-designed, and were vital to the success of the effort to contain the
flooding from the Red River of the North. They were appreciative of the speed of deployment
(vital in emergency situations. such as this), their ability to adapt to irregular subgrades, and the
uniformity of results compared to sandbag dikes. Some cautions oftentimes repeated were to be
careful with proper filling of the barriers, and to pay particular attention to the subgrade the
barriers are placed on, as this can cause significant problems. Additionally, transitions between
Hesco's and other types of dikes need to be done carefully, allowing an adequate overlap to
prevent a weak spot in the resulting dike. Adequate monitoring of the completed barrier wall
must be done, just as for any temporary dike, throughout the emergency period. Most users,
especially those who used them in the field, declared they would use them again, given the same
situation.


Some useful recommendations were made, however, and should be considered by Hesco
Bastion.


           o Consider use of colored hinge pins to join the units together. This would make the
                 visual inspection of finished units easier and faster, particularlyat night (i.e., Were
                 the baskets properly joined during installation?).


           o Additional training. Several users reported receiving only very minimal training in
                 how to properly install the units. This caused considerable problems and delays in
                 getting the various installations properly started, especially as new workers arrived to
                 help.



                                                      6-1
U:\2283\0-\Hesco Bastion Report.doc
           o     Preparation of a Guidance Document for communities considering using the Hesco
                 barriers. Like most products being considered to fight a flood, proper engineering
                 needs to be done prior to installing them. Such a guidance document could be given
                 to communities prior to their using Hesco's, recommending the type of engineering
                 needed, the considerations that need to be made, and procedures to follow for such
                 things as needed site preparation, height of barriers needed for the predicted flood
                 elevations and their configuration (e.g., 2-4' barriers with 1-4' stacked over them, or
                 2-4' with 2 more 4' barriers stacked over them), lessening seepage with plastic
                 sheeting and how to do it (front face of barrier, back face, how anchored, etc.),
                 joining Hesco barrier walls to sandbag or clay dikes (necessary overlap, tie-ins, etc.),
                 and proper installation procedures.




                                                       6-2
U:\2283\01\Hesco Bastion Report.doc
              Attachment A


Red River Flood Protection Plan - 3/26/2009
          (Map of Levee System)
                                                                    -S       _                             "----   A-




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                                        .4
                                              .4.   4   4
                                              4~4                                                                            wo            NAVD 19M 5Ei. Dau0m




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                                         I_
                                         I.
                 Attachment B


     "Engineering  Analysis "from Report to:
United States Senate Committee on Appropriations,
                June 29- 30, 2004
                           Pages 1 and 2 are not included as
                           part of this excerpted document                                    3S

                                  ENGINEERING ANALYSIS'


The ability of the Concertainer®• structure to withstand hydrostatic.and uplift forc•si as
well as other forces, results primarily from a combination of shape and weight of the
structure and the frictional resistance generated along its base. ThMe linkages between the
units also allows for the load on a single unit' to be distributed over several adjacent units.
The structure is compliant and deforms'slightly as a response to0applied loads. This
particularly important when the structure responds to uplifting forces. The
Concertainer® basket is basically ashell and will.experience almost no upliftingforces.
Sifice the basket is• oipen:at the bottom, if the unit is raised the fill material remains in
contact withthe ground surface. The upliftingforce on the fill:will be due to buoyancy
and not' from any mechanical forceWof the basket. Therefore, theconventional, analysis of'
stability based upon overturning is not applicable to-the Concertainer® structure.
However, because the basket and fill'could. be displaced laterally, the analySis of-the
stability of the structure toslidingis appropriate,

The ability ofthe structure to resist lateral forces it~can be theoretically analyzed-based
upon the assumption that the structure will respond as a rigid body to hydrodynamic
forces. A general load 'case~is shown in Figure 1.


                      Fw,:Fi
                          F1      -•    II
                                       .II                      II
               h      Fh     -•         I                    ,11'


                                                  t    t~-Rh,
                                             Fu       Rv

Figure 1. Schematic diagram of forces on a: Concertainer® unit.

The Figure illustrates that the force per foot of structure on'the Concertainer® can result
from several sources:

       W = weight of the basket and fill
       Fhl.= hydrostatic pressure force
       Fw = wave forces
       Fi= impact force
       Fu = uplift' force
       Rv = vertical reaction force:of the soil
       Rh =.horizontal reaction force of the soil with a maximum valueequal to Cf'Rv,
             where, Cf.is the coefficient of friction along the.interface

                                                                       United States Senate
                                                                Committee on Appropriations
                                                                            tJune 29-30. 2004
                                                                                              4



The formulas for the static forces for the load .case shown in Figure 1 and their lines of,
action from point A, are as follows:


         W=   M2yfii   BH                                       @ B1/2
         Fh.= t/ y-h,                                           @ h/3
         Fu = YYB h                                             @02/3 B
         Rv =.W- Fu                                             @ 1/31B
         Rh,-- Fh with maximum value of Cf Rv

Where:
         B = width of :the Concertainer®.
         H:= height of the Concertainer®
         Yii-= unit weight of the filltor S y
         y unit weight of water
         S =specific gravity of the fill
         h, =height of Water. above the base of the structure

The,resistance to sliding can be expressed asa.factor of safety, which is the: ratio of the
resisting forces to the.:appliedforces. The horizontal resistig force isthe frictional
resistancegenerated along the base of the -structure, given by Cf RV. The applied.
hydrostaticlforce is Fh. Thusfactor-of safety against sliding can then be defined by

                 SF = CfRv/Fh = Cff(W-FU)/Fh

The analysis presented is based upon treating the structure asýa rigid body, the
Concertainer® is actuallydeformable and-it would affect the::impact loads and the
overturning. The.Concertainer® is highly resistant toimpact loads because.the basket
ýand fill deformnwhen the load 4s applied,.thus lengthening. the time over which the
impacting object is stopped, anldhence, reducing the force. Thetamount of deformation
would, depend upon the, where the impact'occurred, with more deformation occurring
near the top of thestructure.


The Concertainer® structure is well suited to resist(impact loads. The structure is
:compliant such that it will deform under loads. This property means thatoa unit will
.absorbedebris loads and ,actually:experience a lower force from debris than rigid
 structures would experience for the same debris. This can be explained because debris
.loads resulting from floating objects such as vegetation, logs and, lumber are impact
 loads. In an impact load theý force produced by the impacting objectdepends upon the
 initial momentumbof the object, its mass time ýits velocity, and the time over which the
objects velocity is:reducedto zero by the impact; that,is its deceleration. -Thecompliancy
 of:.the, structure thus extends the-time over which the impactingiobjectis stopped. This
 results in a reduced deceleration and'hencea reduced force onthe structure. The

                                                                        United States Senate
                                                                Committee on Appropriations
                                                                           June 29-30, 2004
                                                                                                   5

'performance of the structure under debrisloads would-also depend uponthe waterdepth
 relative to the top of the structure, the fill in,thestructure and the shape oqf thledebris
 object. Impact tests for specificobjects-!of interest for •various fill types would: need to be
 conducted. The effect of debris loads~on, the performanceof the.:Concertainer® can be
 accounted for by incluiding impact loads inthel analysis of-the factor of safety against
 sliding.

Waves canaffect the Concertainer® structurein several differentmanners: as an
additional horizontaltforce, as a carder of debris, ,and as a mechanism for removing
material from the structure. The effects, of wavesz'wil depend upon whether thewaves
*hitting the structure are non-breaking, breaking or broken waves. TIe horiiontal force on
 a structure produced by each type of wave can be compUted from standard coastal
 engineering design procedures, e.g.;, the: Shore Protection Manual, and:included in the
 analysis of'theresistance:of a structure to~sliding for various unit sizes and types of fill.,
 Debris loads could be severely increased untirdr wave :action. Whilehelil   movement of
 water resulting from a current willfbe generally parallel to the structure, wave.actioný
 causes water movement-that is more generally perpendicular to the structure. The
 Sveloeity'of the water at the crest of a breaking wave approaches the phase speed of the
 wave and, even in shallow water, can reach a value of several feet/sec., Thus velocity of
 the debris:could be greatly increased byltheepresence of waves. The property of the
 Concertainer®,to absorb impact loads clearly'becomes an advantage inresisting this
 wave enhanced threat from debris. The.effect of waves onthe erosionof material from
 the structure will depend upon the height of the mean water-at the structure. thetheight
 and type ofwave hitting the structure,iandthe fill material. When the combined mean
 waterheight ,and incoming waveheightris lower than the.top of thestructureno erosion
 would occur. .For meanwaterlevels below, the top of the structure, but with wave height
 high enough'to overtop the'structure, erosion would b,'e'minimal. Water would be thrown
 onto the top of the.fill with little'horizontal velocity and wet the fill. For higher waves,
 waves: that break into the structure, there,would be'some initial suspension andtransport
 of fill out of the structure. When the meaný Water height exceeds the height of the
 structure so that-,it becomes submerged all 'types o•fwayes would suspend some fill
 material. 'The amount of fill. removed Would depend upon the intensity of the.,wave action
 and the type offilL. These various effects of wave actionon the structure wouldneed to
 be considered inthe selection of the Concertainer® size and fill soas todmaintain.ran
'acceptable factor of safety'against sliding under expected field conditions;




                                                                        United States Senate
                                                                Committee on Appropriations
                                                                           June12930, 2004
                                                                                                6



                        GROUND SURFACE, PERFORMANCE


The performance of the Concertainer@ on various surfaces will depend both on theltype
of surface and the type of fill used in the structure. This is because the same fill will
interact -differently with different surface materials. The.net effect of the surface/fill
interaction can-be expressed through the interfaceýfriction coefficient. As shownwaboye,
the friction coefficient directly affects the resistance of the structure to sliding. Other
factors thatmay need to be considered concerning the surface upon which the structureis!
placed are the-permeability of the surface and it's bearing capacity. Given the test
conditions described in the solicitation,• the bearing capacity and permeability of the test
surfaces should-present no problems. However, in actual usage, these issues would need
to be investigated at eachfield site.

The actual coefficient. of friction between different fill materials and the different test
surfaces will depend upon the detailed characteristics each. Since lthese arenrot known at
this time, representation values of the friction-coefficient can be taken from published
values. 'The following values were used in the stability-analysis:,

Table1. :Soil parameters used imthe analysis.

Fill Type          Specific Gravity           Interface Coefficient of Friction
                                               Earth     Concrete       Grass,
Fine Sand               1.60                    .58         .35           .30
Coarse.Sand             1.76                    .67         .45           J35
Gravel-                 1.92                    .78         .60           .40

The coefficients of friction between concrete-and for variousi fill types are taken from-the
Shore Protection Manual (Table 7-15 and 7-16). Table 7-16 gives-the-friction
coefficients for concrete dams on-sand and gravel. For freshlygraded surfaces, earthen
material is present both in.the container and on the surface. The, friction resistance will
depend upon the angle of internal friction for the each material' Theý values used in-the
analysis for the various fills-on an earthen surface'are based upon the angles of internal
friction for firmly packed sediments as given-in Table 7-15 oflthe-SPM. For the grass
surface case, the approach takenis that the coefficient-,of friction will; be ýassumed. to be
smaller than for a concrete surface. Thus the concrete values Were reduced for gravel,
coarse sand, and frheesand by factorvof .67, .77 and .86 respectively.




                                                                       United States Senate
                                                               Committee-on Appropriations
                                                                          June 219-30, 2004
                                                                                                 7




                        FIELD REPAIR AND MAINTENANCE,

Depends on the location.

                             TEST CONDITION ANALYSIS

The performance of the Concertainer® under aparticular set of test conditions can be
determined using the formulaspresented above. Various loadcases were considered
based upon the type of surface at the, testsite, the height of the floodwater, the size of the
structure and the fillmaterial. The results of these calculations are given in Table'2..

A single.load caseg will be used to illustrate the methodology used in :computing the factor
of safety against sliding. The structure will be assumed to be placed on either grass, ýearth
or concrete. A 3 foot by 3 foot unit will be subject to a 3 foot flood, with no waves or
impact loads. The structure will be fill with either fine sand, coarse sand, or gravel. The
formula for the factor of safety against sliding for a 3 foot'.Concertainer® unit (b=H=3
feet) as

                        FS = Cf ( W-Fu)/Fh
or                                                           2
                FS = Cf (HBSy-hBy/2)/(h yI2) =2BCf (HS-h/2)(h )
                                       2


This can be si'mplified for H =B =3 ft, and h=3 feet to

                        FS= ,67Cf (5S- 1.5)

For-the various fill materials and surface:types the values of Cf and S can belspecified.
For-example, for an earthen surface and with a fine.sand fill, S=- 1.60 and:Cf= .58. The
computed factor of safeay is

                        FS =.67 (.58),(3(L.60))-1.5)= 1.28

This is the result shown' in Table2 forload case 1l. For coarse sandS,= 1.76 and Cf=
.67, and the resulting factor of safety is 1.69, as shown in Table 2 for loadcase2.• For
gravel. S =1.92 and Cf,= .78, and the factor of safety is'2.22, aswshown in Table 2 as load'
case 3.

The other load:cases listed in Table 2 were based upon changing the~surface.;types, flood
water depth and unit size. A second set of calculations were performed based upon
increasing the flood water depth to 4 feet, and placing a 2 foot by 2Tfoot Concertainer®
on top ofa 3 foot by 3 foot unit. The factors of safety against sliding for different
surfaces are given in,load cases 28, :29 and'30.

                                                                       United States Senate
                                                               ;Committee on Appropriations
                                                                           June 29-30, :2004
                                                                                             8

Overall the analysis indicates that for the fill types and surface types considered, large
changes in the factorof safety canoccur. For example, for a3 foot by 3.foot unit on a
concrete surface the factor of safetychanges: from -77 to 1.13, to l.70 as the fill is
changed from fine sand, to coarse sand and thento gravel.
Table 2. Factor of safety against sliding for.various load cases.

Load         Surface      Structure    Flood       Fill                 Factor of Safety
Case          Type          Hgt        Hgt        Type                  Against.Sliding

1              E              3'         3,        FS                         1.28
2              E              3,         3i        CS                         1.69
3              E             .3,         3'        GR                         2.22
.4
               C                         3,        FS                           .77
5              C              3,
                              3,         3,'       :CS                        1.13
               C.                        3,        GR                         :1.70
6                             31
7              G                                    FS
8              G              3,                    CS                          ,.88
                                         3'
                                         3,
9              G,             3,                   GR                          1.14
10             E              4,         3,        FS                         -2.-53
1:1            E              4,         3,        CS                         3.30
               E                         3,        GR                         4.28
12                           4,
               C                         3,        FS                          1.52
137
                              4,         3,)
                                                                              2.22
14             C                                   CS
                              4?
15             C                                   GR                         329
                              4,                                               1.31
16                            4)         3,         FS
1.7.                          4,
                              4'                   Cs                         1.72
               'G'                       3,1
                              4,                   GR                         220
18
19             E              41         4,4        FS                         1.28
20             E              4,         5,
                                         4,         CS,                        1.69'
2-1            E              4,         4,         GR                        2.22
22.            C              4,         4,         FS                         .77'
23:            C              4,         4,         CS                        1.13
24             C              4'         4,         GR                        1-30
25             G              4,         4,         FS                         .66
26             G                         4,4        CS                         .88
27             G             4,
                             4)
                             4'          4,5        GR                        114,
28             E             4,
                             4?'         5,)        FS                        1'07
29             E                         5,         CS                        '1.41
30             E                                    GR                        -1.85

Note: E= Earthen surface
      C.= Concrete surface
      G = Grass surface
      FS-= Fine sand fill
      CS = Coarse-sand fill
      GR = Gravel fill
                                                                        United States Senate
                                                              Committee on Appropriations
                                                                         June 29-30,2004
                                                                                     9


      The data. presented herein by HESCO Bastion USA, LLC from- the Rapid
Deployment Flood Wall Testing at Engineering Research and Development Center
(ERDC) Water Experimental Station (WES) in preliminary information from Dr. Joseph
Suhayda.




                                                               United&States&Senate,
                                                       Committee on Appropriations
                                                                  Juine29-30, 2004
HESCO Bastion USA. Inc.         Tel: 985-345-7332        (1
47152 Conrad E.Anderson Drive   Email: infoghesco-usa.com
Hammond, LA 70401               Web: www.hesco-usa.com




MEMORANDUM

TO: RECIPIENTS OF TECHNICAL REPORTS AND INFORMATION

The information provided by Hesco herewith is intended solely to provide -general guidance to a
purchaser or potential purchaser of its products, who accepts full responsibility for the engineering
and other design, installation and use of structures incorporating the Hesco Concertainer and
associated products. While reasonable care has been taken to ensure that the information
provided is accurate and has been obtained from reliable sources, and the information is provided
in good faith based upon that which is available at the time of production, Hesco provides no
guarantee or warranty as to the accuracy, completeness or effectiveness of the information.
Nothing herein shall be construed as a substitute for the need for the purchaser to exercise or
employ adequate independent technical expertise and judgment. Purchaser acknowledges that
risks and dangers may arise from foreseeable and unforeseeable causes and assumes all risk
and danger and all responsibility for any losses and/or damages to person or property that may
result from purchaser's use of Hesco's products. HESCO PROVIDES NO GUARANTEE OR
WARRANTY, WHETHER EXPRESS OR IMPLIED BY LAW, IN CONNECTION WITH ITS SALE
OR THE THIRD PARTY INFORMATION PROVIDED HEREWITH, INCLUDING WITHOUT
LIMITATION MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, EXCEPT AS
EXPRESSLY STATED IN ITS STANDARD TERMS AND CONDITIONS OF SALE.

				
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